The present invention relates to security/fire alarm systems of the type which are continuously monitored for alarms and other conditions that may require the immediate attention and/or servicing provided by a system-monitoring enterprise. More particularly, it relates to improvements in apparatus for discouraging the repudiation of a contractual arrangement between a system monitoring enterprise and a customer who has agreed to have such enterprise monitor the alarm and/or operating status of the system for a predetermined time period.
A security/fire alarm system dealer, under contract to an end user, will spend considerable time and effort in customizing the installation of a security/fire alarm system to suit the needs of his customer. Depending on the physical size and needs of a building requiring intrusion and/or fire protection, a suitable security/fire alarm system may comprise a wide variety, as well as a large number, of intrusion and fire sensors. These sensors must properly set-up and checked out at key locations throughout the building. Further, they must be connected by wires, referred to as a "bus", to a master control unit which, in the more sophisticated systems, operates to repeatedly interrogate the individual remote sensors by a digital address code which is unique to each remote sensor. Upon being interrogated or "addressed", each sensor transmits a communication to the master control unit indicating its alarm status and whether or not the sensor and its communication electronics are functioning properly. Two-way communication between the control unit and the remote sensors is in the form of digital electronic multiplexed signals and takes place over a communications "bus" which connects all remote sensors with the control unit. A security/fire system of this type is disclosed in the above-referenced U.S. patent application Ser. No. 817,866, filed concurrently herewith, the contents of such application being incorporated herein by reference.
In addition to contracting to install an alarm system, which an alarm system may either lease or sell to the customer, an alarm dealer will often contract with such customer to provide, for a monthly fee, a twenty-four hour per day system-monitoring service. Compared to the installation phase, the monitoring phase is considerably more profitable to the installer, and it is here that the installer can recover a large part of the installation cost. Obviously, the installer would like to monitor the system as long as possible, certainly, at least, for the agreed-upon term of the monitoring contract. However, it is sometimes the case that another system-monitoring enterprise will induce the customer to repudiate his monitoring contract with the installer in favor of a lower monthly service fee offered by the other enterprise. This lower service fee is usually made possible by the fact that the other enterprise has no installation costs to recover. To prevent this occurrence, manufacturers of master control units design them so that the system can only be programmed by a remote dial-in. Thus, to take over the monitoring account, one needs to know the correct phone number, an access code and a password. Since this information is known only to the original installer, unauthorized takeovers are discouraged. But this type of anti-takeover system can still be circumvented at modest cost by merely purchasing an identical control unit from the same manufacturer and connecting it to the existing wiring of an installed system. The enterprise taking over the account can then program the control unit to respond to a new phone number, access code and password.